1. Field of the Invention
The present invention relates to a material and methods for the manufacture and use of same usable in a device to attenuate shock loads and distribute loading and, more particularly, to an improved shock attenuating and/or load distribution material for a device having an outer membrane or displacable structure wherein the material is a viscous colloid formed from a solution of super absorbent polymers and a liquid, such as water, for use in footwear, medical, and other applications.
2. Description of the Prior Art
The search for cost effective shock absorbing and load distribution devices for various applications has been an on-going quest over the years and has resulted in a number of innovations, especially in the athletic footwear and medical fields. These innovations focused on the problems created by impact loads generated during running or walking, as well as the problems created by concentrated loads suffered by ambulatory medical patients and those using prothestic devices.
Running or jumping, especially during activities such as aerobics, causes very high localized loading of the human foot and ankle areas which can contribute to injury of the foot, ankle, associated joints such as foot, ankle and knee joints and leg bones. Consequently, product innovations in this area in recent years have rapidly developed in an effort to alleviate these problems. An added desirable feature of these innovations has been the introduction of comfort and fit improvements in the athletic footwear. Additionally, efforts to relieve the discomfort and localized injury caused by bedridden medical patients and those using load-bearing artificial limbs have been of great interest.
The typical solutions, to date, have included the use of ampules or pads formed from a flexible outer membrane hermetically filled with a liquid of an appropriate viscosity or a gas such as air, which is then inserted into the footwear or medical appliance at locations experiencing the greatest loading. Various membrane materials have been employed, as have a wide range of fillers. Filler liquids have included water, glycol mixtures, various oils and other relatively low viscosity liquids. Furthermore, higher viscosity liquids or gels, in an effort to improve the hydrostatic properties of the liquid, have incorporated semi-solids such as organosiloxane gels as the shock absorbing or load distributing material. Gas fillers have typically used enclosed pockets of air. Whereas in the past these devices used liquids, gels, or air, depending on the desired viscosity, none apparently offered the cost effective shock attenuation and load distribution performance of the present invention.
Therefore, improvements were generally sought to produce shock attenuating and load distribution devices of high durability, low cost, and ready manufacture for use in footwear, medical applications and other applications where the dissipation of load over time and/or an area is desired. To this end, as an aspect of the invention described herein, the feasibility of applying the concept of using super absorbent materials, together with an appropriate liquid, to constitute a low cost viscous colloidal fluid as the shock attenuating and load distribution material was examined. Although the theory and underlying physical phenomena represented by the non-Newtonian fluid of the present invention is now not completely understood, it was discovered that shock attenuating devices formed from a resilient membrane and filled with a super absorbent material and liquid mixture offer excellent performance characteristics in the dissipation and distribution of loading, while simultaneously offering an inexpensive and readily manufacturable product.
Previously, super absorbent materials have long been used in applications to absorb various liquids for ready and efficient disposal in articles such as diapers, sanitary napkins, bedding pads and the like. These super absorbent materials, uniquely suited to such applications, are generally hydrophilic and absorb an enormous quantity of liquid relative to its mass through capillary action.